Referring to FIGS. 1 to 3, FIG. 1 illustrates a conventional liquid crystal display device; FIG. 2 illustrates an optical plate broken or deformed due to a force applied at a steel pillar of a backlight module of the liquid crystal display device of FIG. 1; FIG. 3 illustrates a point contact of an optical film touching with a steel pillar of a backlight module of the liquid crystal display device of FIG. 1.
As shown in FIG. 1, a liquid crystal display device 1 comprises a backlight module 10 and a liquid crystal panel 11. A back plate 100 of the backlight module 10 is normally bent into an n-shape to form for increasing the strength of the back plate. In an extra large size module, the back plate 100 is generally assembled by an aluminum sheet and a metal sheet. When positioning an optical film 101 or an optical plate 102 (e.g., a diffusion plate), because the formation of the aluminum sheet can't be formed by flange-stamping as that of the metal sheet does, the optical film 101 or the optical plate 102 is normally positioned by a steel pillar 103.
As shown in FIG. 2, because a contact between the steel pillar 103 and the other component such as optical sheets is a point contact, a contact area where the steel pillar 103 is in touch with the optical plate 102 is very small. When a vibration happens, the optical plate 102 may subject to a large pressure due to the counteraction force of the steel pillar 103; that is, the stress is concentrated, and the optical plate 102 may be deformed and then broken as shown in the wave lines of FIG. 2. As shown in FIG. 3, the sheet-shaped optical film 101 is hung on the steel pillar 103, which is also a point contact; therefore, when a force is applied to a point of the sheet-shaped optical film 101, the force is split into two components (as shown in the arrow of FIG. 3) under gravity and using the forced point as a center point. That is, sheet-shaped optical film 101 is unable to balance with only one supporting point, such that the optical film 101 may be warped and deformed which leads to a non-uniform illumination in the backlight module.
Moreover, in order to get larger strength, the steel pillar 103 adopted in the backlight module cannot too small, while a space in the backlight module is required for disposing the bottom portion of the steel pillar 103 and riveting and stamping, such that a narrow bezel backlight module can't be realized easily.